An aside comment...when dealing with ADA toilets, they require the handle to be on the 'open' side, so you don't have to reach over the toilet to flush it. So, that is why some toilets are offered with an option.

Jeff, the handles are not interchangeable since they are side mounted. If you have a left hand trip lever, you need a left hand handle. I'm not sure if the right hand handle would even fit on the lever, but if it did, if would point backward. Now on the Dartmouth which is very similar to a Drake, the handles would interchange because they are a different shape. I would suggest you contact Toto and see if they can provide a gold left hand handle for you.